The present invention is directed to an automatic focusing camera, and more particularly to an automatic focusing line scan camera for use in scanning applications.
In scanning applications, for examples for packages traveling along a conveyor, it is often required that scans be carried out at varying target distances. For example, if a larger package moves along a conveyor beneath a scanner, the distance between the lens of the scanning camera system and the object is shorter than for a smaller package traveling along the same conveyor path. Prior known systems generally provide focusing for the scanning camera by adjusting the position of the lens system or the image sensor to focus the image plane on the senor. However, this can result in higher costs for systems employing movement of one or more lens in order to maintain the optical alignment of the lens relative to one another and the sensor. Additionally, movement of the image sensor can add additional complexity and cost due to the need to provide electrical connections to an from the imaging sensor and to maintain the desired orientation of the sensor over the path of movement.
It would be desirable to be able to provide adjustment of the object focal length without the need for moving either the lens system (or one or more lenses therein) or the sensor relative to one another in order to provide a simple and reliable automatic focusing system for a camera system, preferably for use in scanning applications.
Briefly stated, the present invention is an automatic focusing camera which includes an image sensor. A fixed lens system is provided having a lens with an object side and an image side. The fixed lens system is located in a fixed position relative to the image sensor. A mirror is moveably positioned between the image side of the lens system and the image sensor. The mirror is located at an angle such that an image observed through the fixed lens system is reflected toward the image sensor. An actuator is connected to the mirror and moves the mirror relative to the lens system to change a distance between the lens system and the image sensor to adjust an object focal length between an object and the camera.
In another aspect, the present invention provides a method for automatic focusing of a camera having an image sensor and a lens system with an objective lens located at a fixed position relative to the image sensor. The method comprises: (a) providing a mirror moveably mounted between an image side of the lens system and the image sensor; and (b) adjusting the position of the mirror to vary a length of an optical path between the image sensor and the lens system to vary an object focal point on an object being observed.